Post-doctoral position beamline PSICHE and ANATOMIX (Tomography and Imagery)

Located in the heart of the Paris-Saclay cluster, some twenty kilometers from Paris, SOLEIL is the French synchrotron radiation source. In this Very Large Research Infrastructure, the experiments are based on the use of a light radiation produced by electron bunches circulating almost at the speed of light in a ring. This exceptionally bright radiation covers a very wide range of wavelengths: from infrared to X-rays, including ultraviolet. Its characteristics (intensity, focus, stability, etc.) make it possible to observe matter at all scales, down to the atom, for experiments in both fundamental and applied research or of industrial interest. Since 2008, SOLEIL has served many fields that mobilize science and industry today: physics, biology, chemistry, materials science, the environment, Earth sciences or cultural heritage. SOLEIL is placed under the joint supervision of the CNRS and the CEA, and offers its staff a multidisciplinary and international working environment.

The SOLEIL II project is an ambitious upgrade of the entire facility, which will enable experiments up to ten thousand times faster, a thousand times more sensitive, with nanometer-scale resolution ..., and thus make a decisive contribution to many societal challenges, in research on advanced materials, energy and sustainable development, health and well-being, the environment ....
The first supplies for the construction of SOLEIL II begin in 2024. The current facility will continue to operate in parallel until autumn 2028. Startup of SOLEIL II is scheduled for 2030, with a ramp-up until 2035.

SOLEIL is a partner in the Franco-German project AIQuAM3D. This project aims to apply artificial intelligence to additive manufacturing by laser-powder bed fusion (L-PBF). At SOLEIL, synchrotron X-ray microtomography will be used to characterize the defects in L-PBF printed components. Software tools will be developed to analyse this tomography data in near real time, using conventional algorithms and artificial intelligence as appropriate to obtain the best results.  The analysis will reveal both the characteristics of the studied samples (defect sizes, locations, types, etc.) but also give feedback on the instrument settings (alignment problems, signal-to-noise ratio, contrast, spatial resolution, etc.). 
Synchrotron SOLEIL seeks to hire a postdoc in materials science and/or computing for the AIQuAM3D project. The position is based on the ANATOMIX and PSICHE beamlines. It will start in June 2024 at the latest and will last 24 months.
The ANATOMIX (Advanced Nanotomography and Imaging with Coherent X-rays) beamline provides X-ray tomography on the micro- and nanoscale, in absorption and phase contrast. It operates in the energy range between 5 and 50 keV and allows its users to obtain two- and three-dimensional radiographic images of bulk volume samples of macroscopic size (up to several cm thickness). For smaller samples, a spatial resolution down to 50 nm (20 nm pixel size) can be achieved. Real-time studies are possible at speeds of currently up to one microtomography scan per second; higher speeds up to 20 volume scans per second (50 ms per scan) have been demonstrated.
The PSICHÉ (Pressure Structure and Imaging by Contrast at High Energy) beamline is dedicated to X-ray diffraction under extreme conditions (pressure-temperature) and to tomography at high energy, from ambient to extreme conditions. The source is an in-vacuum wiggler that is used to produce a wide variety of beam modes, from a large parallel white/pink beam to a microfocused monochromatic beam. We have two hutches, one dedicated to white/pink beam (energy range: 15-100+ keV) and another to monochromatic beam (20-50 keV). Imaging experiments can be performed in both configurations depending on requirements. 
For both beamlines, the scope of the scientific cases is very large: from biology and paleontology to materials science, high-pressure physics and geophysics.

I. Mission

The postdoc will work on the ANATOMIX and PSICHÉ beamlines under the joint supervision of Andrew King (PSICHE beamline scientist, imaging coordinator) and Timm Weitkamp (ANATOMIX beamline manager).
She/He will actively participate to the user-support program (X-ray computed tomography and materials science) and will be involved in the scientific, technical, and methodological activities of the beamlines. That means preparing the beamlines for the experiments, helping the users with the management of experimental setups, data acquisition and data treatment if necessary.
She/He will develop the AIQuAM3D research program (see next section). She/He will be granted in-house research beam time while also submitting proposals to the peer review committees. She/He will publish her/his results and present them at national and international conferences.  She/He may also pursue their own research interests and collaborations in addition to this program.

II. Responsibility and Tasks

The postdoc will work on two main topics:
•    Characterisation of defects in additively manufactured specimens
In Laser-based Powder Bed Fusion (L-PBF), the additive manufacturing (AM) process with the highest industrial maturity and spread, there are more than 50 adjustable process parameters that influence parts quality. Despite increasing scientific effort, the L-PBF process chain still cannot be fully simulated with state-of-the-art tools, making quality inspection even more important, especially for safety-critical application areas such as the aerospace, automotive and medical sectors. For this, the support of μCT is needed because there is no other method to provide local part density information in a non-destructive, fast and economic manner. In this project an AI-model will be developed to correlate multiple features generated from L-PBF in-situ monitoring data with defect labels obtained by μCT. The ultimate goal is to implement an embedded model for real-time defect prediction in a L-PBF system and validate it for reference samples and a complex geometry demonstrator. The post-doc will contribute to these studies via μCT studies of AM parts.  
•    Development of software tools for real-time tomography reconstruction and data analysis
μCT is widely used as a tool to investigate three-dimensional morphology of materials in industrial research and development (R&D) and non-destructive testing. Synchrotron-based μCT is capable of very fast data acquisition at high spatial resolution, allowing in-situ imaging and high sample throughput. However, so far synchrotron μCT has remained mainly an R&D tool despite its advantages. One obstacle to its wider adoption is the delay between the design of an experiment and the final result. This is partly due to the quantity of data, which is often the bottleneck in the pipeline between data collection and result: the number of 3D image volumes can exceed 100 samples per 8-hour shift, and the corresponding data volume can be over 1 TB per hour of beamtime. Additionally, access to synchrotron facilities is more limited than for conventional μCT scanners: measurement campaigns typically must be planned weeks or months ahead, and beamtimes are short and require stringent preparation and execution. As a result, scan failures due to technical problems or mistakes during the acquisition can put at risk the success of the campaign altogether, unless the error is immediately discovered during the experiment. To ensure the efficient use of synchrotron beamtime for high-throughput analyses, real-time analysis or at least near-real-time automatic quality control of the acquired scan volumes would therefore be a tremendous advantage. In this project software tools (both conventional and using artificial intelligence) will be developed to automate and streamline both data analysis and data quality control/instrument feedback.

III. Education and Experience

The candidate should hold a PhD in mechanics of materials / physics applied to material science or equivalent and have experience in tomography imaging. His/her skills must also include image and volume data processing with Python or some other language, as well as knowledge in AI modelling, training and inference.
The postdoc will join an enthusiastic and growing pluri-disciplinary team, benefiting from multiple national and international partnerships including the AIQuAM3D project.
We’re looking for someone curious, dynamic, autonomous, and who enjoys working in a team.

IV. General conditions

This is a 2-year position.
The position is localized at the SOLEIL synchrotron site (Paris-Saclay campus, Saint-Aubin, www.synchrotron-soleil.fr). 
The assistance to users imposes some on-call duty periods (typically 6 days per semester in average, including one weekend) and may require, in case of need, on-site interventions outside regular working hours.
Contacts:
Andrew KING (Imaging coordinator; beamline scientist PSICHÉ): andrew.king@synchrotron-soleil.fr
Timm WEITKAMP (Beamline manager and scientist  ANATOMIX): timm.weitkamp@synchrotron-soleil.fr